U.S. patent application number 10/622315 was filed with the patent office on 2004-03-18 for exhaust pipe collecting structure of multiple cylinder engine and personal watercraft.
Invention is credited to Matsuda, Yoshimoto.
Application Number | 20040050039 10/622315 |
Document ID | / |
Family ID | 31934132 |
Filed Date | 2004-03-18 |
United States Patent
Application |
20040050039 |
Kind Code |
A1 |
Matsuda, Yoshimoto |
March 18, 2004 |
Exhaust pipe collecting structure of multiple cylinder engine and
personal watercraft
Abstract
An exhaust pipe collecting structure for a multi-cylinder engine
unit having multiple cylinders comprises a first exhaust pipe group
and a second exhaust pipe group, each of which is comprised of two
exhaust pipes selected from four exhaust pipes respectively
connected to the four cylinders; a first exhaust sub-collecting
pipe cast integrally with the first exhaust pipe group, a second
exhaust sub-collecting pipe cast integrally with the second exhaust
pipe group, a first joint portion located at a downstream end
portion of the first exhaust sub-collecting pipe, and a second
joint portion located at a downstream end portion of the second
exhaust sub-collecting pipe.
Inventors: |
Matsuda, Yoshimoto;
(Kobe-shi, JP) |
Correspondence
Address: |
KOLISCH HARTWELL, P.C.
520 S.W. YAMHILL STREET
SUITE 200
PORTLAND
OR
97204
US
|
Family ID: |
31934132 |
Appl. No.: |
10/622315 |
Filed: |
July 18, 2003 |
Current U.S.
Class: |
60/323 ;
60/322 |
Current CPC
Class: |
F01N 13/10 20130101;
F01N 13/12 20130101; Y02T 10/20 20130101; F01N 2590/022 20130101;
F02B 61/045 20130101; F01N 13/004 20130101; Y02T 10/12 20130101;
F01N 3/046 20130101 |
Class at
Publication: |
060/323 ;
060/322 |
International
Class: |
F01N 007/10; F01N
007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2002 |
JP |
2002-210699 |
Claims
What is claimed is:
1. An exhaust pipe collecting structure for a multi-cylinder engine
unit having multiple cylinders, in which exhaust pipes extend from
at least four cylinders of the multiple cylinders and are collected
into one exhaust passage at a location downstream in a flow of
exhaust gases, the structure comprising: a first exhaust pipe group
and a second exhaust pipe group each of which is comprised of two
exhaust pipes selected from four exhaust pipes respectively
connected to the four cylinders; a first exhaust sub-collecting
pipe cast integrally with the first exhaust pipe group; a second
exhaust sub-collecting pipe cast integrally with the second exhaust
pipe group; a first joint portion located at a downstream end
portion of the first exhaust sub-collecting pipe; and a second
joint portion located at a downstream end portion of the second
exhaust sub-collecting pipe, wherein the first joint portion and
the second joint portion are joined to each other to allow the
exhaust gases discharged from the four exhaust pipes to be led into
one exhaust passage.
2. The exhaust pipe collecting structure according to claim 1,
wherein the first joint portion has a first semicylindrical
peripheral wall opened toward the second joint portion with a
parting line extending along a direction of the flow of the exhaust
gases, the second joint portion has a second semicylindrical
peripheral wall opened toward the first joint portion with a
parting line extending along a direction of the flow of the exhaust
gases, and the first and second semicylindrical peripheral walls
are joined to be formed into the one exhaust passage such that an
opening of the first joint portion and an opening of the second
joint portion face each other and the direction of the flow of
exhaust gases of the first joint portion corresponds with the
direction of the flow of exhaust gases of the second joint
portion.
3. The exhaust pipe collecting structure according to claim 2,
further comprising a rubber tube that covers an outer periphery of
the first and second semicylindrical peripheral walls that are
joined to face each other.
4. An exhaust pipe collecting structure for a multi-cylinder engine
unit having multiple cylinders, in which exhaust pipes extend from
at least four cylinders of the multiple cylinders and are collected
into one exhaust passage at a location downstream of the exhaust
pipes in a flow of exhaust gases, the structure comprising: a first
exhaust pipe group and a second exhaust pipe group each of which is
comprised of two exhaust pipes selected from four exhaust pipes
respectively connected to the four cylinders; a first exhaust
sub-collecting pipe cast integrally with the first exhaust pipe
group; a second exhaust sub-collecting pipe cast integrally with
the second exhaust pipe group; a first joint portion located at a
downstream end portion of the first exhaust sub-collecting pipe;
and a second joint portion located at a downstream end portion of
the second exhaust sub-collecting pipe, the first and second joint
portions respectively having outer walls joined to each other to
allow exhaust passages of the first and second joint portions to be
defined by the outer walls, wherein the first joint portion and the
second joint portion are joined to each other to allow the first
and second exhaust sub-collecting pipes to be integral with each
other as seen from outside, an exhaust gas discharged from the
first exhaust pipe group is led into the exhaust passage of the
first joint portion and an exhaust gas discharged from the second
exhaust pipe group is led into the exhaust passage of the second
joint portion, and exhaust passages inside the joint portions are
arranged adjacently.
5. The exhaust pipe collecting structure according to claim 4,
further comprising a connecting tube located downstream of the
first and second joint portions, for collecting the exhaust gases
flowing through the exhaust passages inside the first and second
joint portions.
6. The exhaust pipe collecting structure according to claim 5,
wherein the connecting tube is cast by a mold with a two-part
parting line extending along a longitudinal direction of the
connecting tube.
7. The exhaust pipe collecting structure according to claim 6,
wherein the first and second exhaust sub-collecting pipes and the
connecting tube have double-walled structures to have cooling
passages between walls.
8. An exhaust pipe collecting structure for a multi-cylinder engine
unit having multiple cylinders, in which exhaust pipes extend from
cylinders of the multiple cylinders and are collected into one
exhaust passage at a location downstream of the exhaust pipes in a
flow of exhaust gases, the structure comprising: connecting tube;
and an exhaust manifold attached on the connecting tube, the
exhaust manifold including: a first exhaust sub-collecting pipe and
a second exhaust sub-collecting pipe located on downstream portions
of exhaust pipes extending from the cylinders, the first and second
exhaust sub-collecting pipes being configured to have internal
independent exhaust passages of the exhaust gases flowing from the
exhaust pipes, the first and second exhaust sub-collecting pipes
being integral with each other at least at their joint portions as
seen from outside; and a first water jacket formed at the joint
portions to have a water flow cross-section elongate in a direction
perpendicular to a casting parting plane forming a boundary of the
first and second exhaust sub-collecting pipes as seen in a
cross-sectional view.
9. The exhaust pipe collecting structure according to claim 8,
wherein the multiple cylinders are four cylinders, the first
exhaust sub-collecting pipe is configured to have internal
independent exhaust passages of the exhaust pipes of two cylinders
selected from the four cylinders, and the second exhaust
sub-collecting pipe is configured to have internal independent
exhaust passages of the exhaust pipes of the remaining two
cylinders, the first water jacket is formed at the joint portions
where the first and second exhaust sub-collecting pipes are
integral with each other, to have the water flow cross-section that
is elongate in a direction from a region between the two exhaust
pipes of the first exhaust sub-collecting pipe to a region between
the two exhaust pipes of the second exhaust sub-collecting pipe so
as to cross the casting parting plane forming the boundary of the
first and second exhaust sub-collecting pipes as seen in a
cross-sectional view.
10. The exhaust pipe collecting structure according to claim 9,
wherein the exhaust pipe collecting structure is integrally cast by
locating the casting parting plane of the exhaust pipe collecting
structure within one continuous plane.
11. The exhaust pipe collecting structure according to claim 8,
wherein the connecting tube comprises: a plurality of connecting
exhaust passages communicating with the exhaust pipes of the
exhaust manifold and being merged into a single exhaust passage;
and a second water jacket extending to a position upstream of the
single exhaust passage so as to substantially define two groups of
the connecting exhaust passages.
12. The exhaust pipe collecting structure according to claim 11,
wherein the connecting exhaust passages are collected at a location
inside the connecting tube provided downstream of the exhaust
manifold having the exhaust pipes.
13. The exhaust pipe collecting structure according to claim 12,
wherein the first water jacket is formed in part of the exhaust
sub-collecting pipes so as to substantially define exhaust passages
of the exhaust sub-collecting pipes as seen in a cross-sectional
view, and at a connecting portion between the exhaust manifold and
the connecting tube, the first water jacket of the exhaust manifold
is connected to the second water jacket of the connecting tube such
that a longitudinal axis of a water flow cross-section of the first
water jacket of the exhaust manifold crosses a longitudinal axis of
a water flow cross-section of the second water jacket of the
connecting tube.
14. The exhaust pipe collecting structure according to claim 13,
wherein a water flow portion where the water flow cross-section of
the first water jacket of the exhaust manifold and the water flow
cross-section of the second water jacket of the connecting tube
overlap with each other with their longitudinal axes crossing each
other is enlarged.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an exhaust pipe collecting
structure obtained by extending exhaust pipes from exhaust ports of
cylinders of a multi-cylinder engine, for example, a four-cylinder
engine, and by collecting these exhaust pipes, and a personal
watercraft (PWC) which is equipped with the engine having the
exhaust pipe collecting structure and is configured to eject water
rearward and plane on a water surface as the resulting
reaction.
[0003] 2. Description of the Related Art
[0004] A multi-cylinder engine unit, for example, a four-cylinder
engine unit, is mounted as a motor in various vehicles including
jet-propulsion personal watercraft. In recent years, the
jet-propulsion personal watercraft have been widely used in
leisure, sport, rescue activities, and the like. The personal
watercraft is configured to have a water jet pump that pressurizes
and accelerates water sucked from a water intake generally provided
on a bottom hull surface and ejects it rearward from an outlet
port. As the resulting reaction, a body of the jet-propulsion
personal watercraft is propelled. In the jet-propulsion personal
watercraft, a steering nozzle provided behind the outlet port of
the water jet pump is swung either to the right or to the left by
operating a bar-type steering handle to the right or to the left,
to change the ejection direction of the water to the right or to
the left, thereby turning the watercraft to the right or to the
left.
[0005] In a multi-cylinder engine unit, such as the four-cylinder
engine unit, exhaust pipes extend from exhaust ports of the
cylinders and are collected into one exhaust passage, and a
downstream end of the exhaust passage is connected to a muffler. An
exhaust gas is discharged outside through the muffler. Such a
multi-cylinder engine unit typically uses an exhaust pipe
collecting structure in which a plurality of exhaust pipes (four or
more pipes) are collected into one exhaust passage in the vicinity
of the engine. The exhaust pipe collecting structure is generally
formed in an exhaust manifold.
[0006] When an exhaust pipe collecting structure is accommodated in
a relatively wide engine room such as in an automobile, the four
exhaust pipes may be formed having a two-part parting plane that is
one continuous plane and passes through the location where the
exhaust pipes are collected. The continuous plane may be a flat,
but is not necessarily so. However, when the exhaust pipe
collecting structure is accommodated in a limited space around the
engine of the personal watercraft or small all-terrain vehicle,
exhaust efficiency and efficient use of the space should be taken
into account. This makes it difficult for the parting plane of the
exhaust pipes to be located on one continuous plane, passing
through the location where the exhaust pipes are collected.
Consequently, casting using a mold also becomes difficult.
[0007] In addition, in the personal watercraft, extension of the
total length of the exhaust passages, which leads to higher
performance of the engine unit, is not accomplished because of the
limited space. Alternatively, in order to produce the same effects
obtained by extension of the exhaust passages by surrounding the
exhaust passage with a water jacket, the temperature of the exhaust
passages is reduced to cause a sound speed of exhaust gases flowing
inside the exhaust passages to be reduced. However, to form the
water jacket, it is necessary to form a double-walled structure in
the exhaust pipes and the exhaust passages, which requires more
complex technology of casting using the mold.
[0008] As described above, when the parting plane of the exhaust
pipe collecting structure is not located on one continuous plane in
casting, casting using the mold becomes difficult. As another
alternative solution to this, steel pipes are welded to be formed
into the exhaust pipe collecting structure. In this case, because a
plurality of parts (e.g., pipe members) having complex shapes are
welded, productivity is reduced as compared to the exhaust pipe
collecting structure cast using the mold. In addition, in order to
manufacture the exhaust pipe collecting structure having the
double-walled structure to form the water jacket around the exhaust
passage, difficult works need to be conducted.
[0009] Further, in the exhaust pipe collecting structure, at a
joint portion where the exhaust passages of the exhaust pipes are
collected into one exhaust passage or in the vicinity thereof, the
shapes of the exhaust passages having an equal total length are
varied from one another. In this structure, the variation in the
shapes of the arranged exhaust passages makes the entire exhaust
pipe collecting structure bulky, which imposes limitation on
arrangement of the water jacket.
SUMMARY OF THE INVENTION
[0010] The present invention addresses the above-described
conditions, and an object of the present invention is to provide an
exhaust pipe collecting structure having a double-walled structure
provided with a water jacket on its periphery, which is
manufactured by casting using a mold. Another object of the present
invention is to provide an exhaust pipe collecting structure having
a dimension reduced in a desired direction while maintaining
cooling capability. A further object of the present invention is to
provide an exhaust pipe collecting, structure provided with a water
jacket having high cooling capability regardless of arrangement of
collected exhaust pipes at a location where exhaust pipes of
cylinders are joined to one another or at a location spaced apart
therefrom. A further object of the present invention is to provide
a personal watercraft that uses the exhaust pipe collecting
structure and has a high exhaust efficiency.
[0011] According to the present invention, there is provided an
exhaust pipe collecting structure for a multi-cylinder engine unit
having multiple cylinders (four or more cylinders), in which
exhaust pipes extend from at least four cylinders of the multiple
cylinders and are collected into one exhaust passage at a location
downstream in a flow of exhaust gases, the structure comprising a
first exhaust pipe group and a second exhaust pipe group, each of
which is comprised of two exhaust pipes selected from four exhaust
pipes respectively connected to the four cylinders; a first exhaust
sub-collecting pipe cast integrally with the first exhaust pipe
group; a second exhaust sub-collecting pipe cast integrally with
the second exhaust pipe group; a first joint portion located at a
downstream end portion of the first exhaust sub-collecting pipe;
and a second joint portion located at a downstream end portion of
the second exhaust sub-collecting pipe, wherein the first joint
portion and the second joint portion are joined to each other to
allow the exhaust gases discharged from the four exhaust pipes to
be led into one exhaust passage.
[0012] In accordance with the exhaust pipe collecting structure so
configured, two-part parting planes of the first and second exhaust
sub-collecting pipes into which the exhaust pipes of at least four
cylinders partially forming the exhaust pipe collecting structure
are collected, are each located on one continuous plane. Therefore,
the first and second exhaust sub-collecting pipes can be cast using
a two-part mold. Since the two-part parting plane is located on one
continuous plane, a double-walled structure provided with a water
jacket around the exhaust passage is formed in the exhaust pipe
collecting structure by inserting cores into an inside of the
two-part mold. In addition, at downstream end portions of the first
and second exhaust sub-collecting pipes, first and second joint
portions are formed to join these downstream end portions into one
exhaust passage. Therefore, by merely joining the first and second
joint portions to each other, one exhaust passage is easily formed.
Further, when the exhaust pipe collecting structure is removed from
the engine, the structure is disassembled into the first and second
exhaust sub-collecting pipes by releasing the joint of the first
and second joint portions, and thereafter, the first and second
exhaust sub-collecting pipes are each removed as individual
members.
[0013] The exhaust pipe collecting structure gains high exhaust
efficiency. In addition, the exhaust pipe collecting structure
having the water jacket on its periphery can be easily cast using
the mold. The exhaust pipe collecting structure achieves high
performance and productivity.
[0014] Preferably, in the exhaust pipe collecting structure, the
first joint portion has a first semicylindrical peripheral wall
opened toward the second joint portion with a parting line
extending along a direction of the flow of the exhaust gases, the
second joint portion has a second semicylindrical peripheral wall
opened toward the first joint portion with a parting line extending
along a direction of the flow of the exhaust gases, and the first
and second semicylindrical peripheral walls are joined to be formed
into the one exhaust passage such that an opening of the first
joint portion and an opening of the second joint portion face each
other and the direction of the flow of exhaust gases of the first
joint portion corresponds with the direction of the flow of exhaust
gases of the second joint portion.
[0015] Preferably, the exhaust pipe collecting structure further
comprises a rubber tube that covers an outer periphery of the first
and second semicylindrical peripheral walls that are joined to face
each other. In this structure, a space between the rubber tube and
the peripheral walls serves as the water jacket. In particular, at
the parting plane, water leakage from the joint faces should be
inhibited. By forming the water jackets with the rubber tube
covering the outer periphery, water leakage to the outside is
effectively inhibited.
[0016] According to the present invention, there is provided an
exhaust pipe collecting structure for a multi-cylinder engine unit
having multiple cylinders, in which exhaust pipes extend from at
least four cylinders of the multiple cylinders and are collected
into one exhaust passage at a location downstream of the exhaust
pipes in a flow of exhaust gases, the structure comprising a first
exhaust pipe group and a second exhaust pipe group each of which is
comprised of two exhaust pipes selected from four exhaust pipes
respectively connected to the four cylinders; a first exhaust
sub-collecting pipe cast integrally with the first exhaust pipe
group; a second exhaust sub-collecting pipe cast integrally with
the second exhaust pipe group; a first joint portion located at a
downstream end portion of the first exhaust sub-collecting pipe;
and a second joint portion located at a downstream end portion of
the second exhaust sub-collecting pipe, the first and second joint
portions respectively having outer walls joined to each other to
allow exhaust passages of the first and second joint portions to be
defined by the outer walls, wherein the first joint portion and the
second joint portion are joined to each other to allow the first
and second exhaust sub-collecting pipes to be integral with each
other as seen from outside, an exhaust gas discharged from the
first exhaust pipe group is led into the exhaust passage of the
first joint portion and an exhaust gas discharged from the second
exhaust pipe group is led into the exhaust passage of the second
joint portion, and exhaust passages inside the joint portions are
arranged adjacently.
[0017] In accordance with the exhaust pipe collecting structure,
two-part parting planes of the first exhaust sub-collecting pipe
and the second exhaust sub-collecting pipe formed by collecting
exhaust pipes of at least four cylinders partially forming the
exhaust pipe collecting structure are each present on one
continuous plane. As a result, the first exhaust sub-collecting
pipe and the second exhaust pipe collecting pipe are cast using a
mold. Since the two-part parting plane is located on one continuous
plane, a double-walled structure provided with a water jacket
around the exhaust passage is formed in the exhaust pipe collecting
structure by inserting cores into the two-part mold. In addition,
at the downstream end portions of the first exhaust sub-collecting
pipe and the second exhaust sub-colleting pipe, the first and
second joint portions have the outer walls (joint faces) by which
the downstream end portions are joined to form two adjacent exhaust
passages. Therefore, by joining the first and second joint portions
to bring their outer walls into contact with each other, the
exhaust sub-collecting pipes are formed into the two adjacent
exhaust passages. Further, when the exhaust pipe collecting
structure is removed from the engine, the structure is disassembled
into the first and second exhaust sub-collecting pipes by releasing
the joint of their outer walls and, thereafter, the first and
second exhaust sub-collecting pipes are each removed as individual
members. The exhaust pipe collecting structure gains high exhaust
efficiency. In addition, the structure having the water jacket in
its periphery can be easily cast using the mold. The exhaust pipe
collecting structure achieves high performance and
productivity.
[0018] Preferably, the exhaust pipe collecting structure further
comprises a connecting tube located downstream of the first and
second joint portions, for collecting the exhaust gases flowing
through the exhaust passages inside the first and second joint
portions. With the connecting tube, four exhaust pipes are
collected into one exhaust passage.
[0019] Preferably, in the exhaust pipe collecting structure, the
connecting tube is cast by a two-part mold with a parting line
extending along a longitudinal direction of the connecting tube. In
this structure, the connecting tube is easily connected to the
downstream end portions of the two adjacent exhaust passages. As a
result, the exhaust pipe collecting structure is easily attached to
and removed from the engine within a limited space of the engine
room. Moreover, the connecting tube is easily cast using the mold
and is formed to have the double-walled structure.
[0020] Preferably, in the exhaust pipe collecting structure, the
first and second exhaust sub-collecting pipes and the connecting
tube have double-walled structures to have cooling passages between
walls. The cooling passages allows the exhaust gases in the
connecting tube to be effectively cooled. With the cooling
passages, an exhaust system gains high exhaust efficiency achieved
by extension of the total length of the exhaust passages.
[0021] According to the present invention, there is further
provided an exhaust pipe collecting structure for a multi-cylinder
engine unit having multiple cylinders, in which exhaust pipes
extend from cylinders of the multiple cylinders and are collected
into one exhaust passage at a location downstream of the exhaust
pipes in a flow of exhaust gases, the structure comprising a
connecting tube; and an exhaust manifold attached on the connecting
tube, the exhaust manifold including a first exhaust sub-collecting
pipe and a second exhaust sub-collecting pipe located on downstream
portions of exhaust pipes extending from the cylinders, the first
and second exhaust sub-collecting pipes being configured to have
internal independent exhaust passages of the exhaust gases flowing
from the exhaust pipes, the first and second exhaust sub-collecting
pipes being integral with each other at least at their joint
portions as seen from outside; and a first water jacket formed at
the joint portions to have a water flow cross-section elongate in a
direction perpendicular to a casting parting plane forming a
boundary of the first and second exhaust sub-collecting pipes as
seen in a cross-sectional view.
[0022] In accordance with the exhaust pipe collecting structure,
the water jacket that is elongate in the direction perpendicular to
the casting parting plane, for increased surface area of the water
jacket, has sufficient cooling capability and, because of the
absence of the water jacket between the two exhaust sub-collecting
pipes, it is possible to reduce the dimension of the exhaust pipe
collecting structure in the direction in which the two exhaust
sub-collecting pipes are arranged.
[0023] Preferably, in the exhaust pipe collecting structure, the
multiple cylinders are four cylinders, the first exhaust
sub-collecting pipe is configured to have internal independent
exhaust passages of the exhaust pipes of two cylinders selected
from the four cylinders, and the second exhaust sub-collecting pipe
is configured to have internal independent exhaust passages of the
exhaust pipes of the remaining two cylinders, the first water
jacket is formed at the joint portions where the first and second
exhaust sub-collecting pipes are integral with each other, to have
the water flow in a cross-section that is elongate in a direction
from a region between the two exhaust pipes of the first exhaust
sub-collecting pipe to a region between the two exhaust pipes of
the second exhaust sub-collecting pipe so as to cross the casting
parting plane forming the boundary of the first and second exhaust
sub-collecting pipes as seen in a cross-sectional view.
[0024] In accordance with the exhaust pipe collecting structure,
the water jacket that is elongate in the direction perpendicular to
the casting parting plane, for increased surface area of the water
jacket, has sufficient cooling capability and, because of the
absence of a water jacket between the first and second exhaust
sub-collecting pipes, it is possible to reduce the dimension of the
exhaust pipe collecting structure. As a result, the exhaust pipe
collecting structure having a three-dimensional configuration is
accommodated in a narrow space. In the exhaust pipe collecting
structure so configured, the dimension of the exhaust pipe
collecting structure protruded from the side portion of the engine
is reduced and, therefore, such a structure is favorably employed
in the personal watercraft having a limited lateral space.
[0025] Preferably, in the exhaust pipe collecting structure, the
exhaust pipe collecting structure is integrally cast by locating
the casting parting plane of the exhaust pipe collecting structure
within one continuous plane. Thereby, it is possible to achieve the
exhaust pipe collecting structure provided with a water jacket
having a desired water flow cross-sectional area regardless of
variation in the shapes of the arranged exhaust passages.
[0026] Preferably, in the exhaust pipe collecting structure, the
connecting tube comprises a plurality of connecting exhaust
passages communicating with the exhaust pipes of the exhaust
manifold and being merged into a single exhaust passage; and a
second water jacket extending to a position upstream of the single
exhaust passage so as to substantially define two groups of the
connecting exhaust passages.
[0027] In this structure, by positioning the merging point of
connecting exhaust passages on the downstream side, the water
jacket can be extended to the vicinity of the merging point of the
connecting exhaust passages. Therefore, the exhaust pipe collecting
structure having high cooling capability is achieved without being
affected by arrangement of the exhaust passages.
[0028] Preferably, in the exhaust pipe collecting structure, the
connecting exhaust passages are collected at a location inside the
connecting tube provided downstream of the exhaust manifold having
the exhaust passages. Alternatively, part of the connecting exhaust
passages may be collected at a location inside the exhaust manifold
provided upstream of the connecting tube as seen from outside.
[0029] Preferably, in the exhaust pipe collecting structure, the
first water jacket is formed in part of the exhaust sub-collecting
pipes so as to substantially define exhaust passages of the exhaust
sub-collecting pipes as seen in a cross-sectional view, and at a
connecting portion between the exhaust manifold and the connecting
tube, the first water jacket of the exhaust manifold is connected
to the second water jacket of the connecting tube such that a
longitudinal axis of a water flow cross-section of the first water
jacket of the exhaust manifold crosses a longitudinal axis of a
water flow cross-section of the second water jacket of the
connecting tube. In this structure, the dimension of the exhaust
manifold protruded from the side portion of the engine is reduced
and the cooling water flows to the downstream end portion of the
connecting tube.
[0030] Preferably, in the exhaust pipe collecting structure, a
water flow portion, where the water flow cross-section of the first
water jacket of the exhaust manifold and the water flow
cross-section of the second water jacket of the connecting tube
overlap with each other with their longitudinal axes crossing each
other, is enlarged. In other words, at the position where the first
water jacket of the exhaust manifold and the second water jacket of
the connecting tube are connected to each other, the water flow
portion is partially enlarged. In this structure, at the position
where the two water jackets are connected to each other with their
longitudinal axes crossing each other, sufficient water flows.
[0031] The above and further objects and features of the invention
will more fully be apparent from the following detailed description
with accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a side view of an engine unit having an exhaust
pipe collecting structure according to an embodiment of the present
invention, as seen from the side on which exhaust pipes are
arranged; and is a view taken in the direction of arrows along line
I-I in FIG. 27;
[0033] FIG. 2 is a view taken in the direction of arrows along line
II-II in FIG. 1, showing the engine unit in FIG. 1 mounted in the
personal watercraft;
[0034] FIG. 3 is an enlarged side view showing a configuration of
the exhaust pipe collecting structure in FIG. 1;
[0035] FIG. 4 is a view taken in the direction of arrows along line
IV-IV in FIG. 3, showing a structure of joint portions of
downstream ends of the exhaust pipe collecting structure;
[0036] FIG. 5 is a side view showing a structure of a first exhaust
sub-collecting pipe of the exhaust pipe collecting structure in
FIGS. 1 and 3;
[0037] FIG. 6 is a side view showing a structure of a second
exhaust sub-collecting pipe of the exhaust pipe collecting
structure in FIGS. 1 and 3;
[0038] FIG. 7 is a view taken in the direction of arrows along line
VII-VII in FIGS. 5 and 6, showing a portion where the first and
second exhaust sub-collecting pipes in FIGS. 5 and 6 are
merged;
[0039] FIG. 8 is a side view showing another structure of the first
exhaust sub-collecting pipe of the exhaust pipe collecting
structure in FIGS. 1 and 3;
[0040] FIG. 9 is a side view showing another structure of the
second exhaust sub-collecting pipe of the exhaust pipe collecting
structure in FIGS. 1 and 3;
[0041] FIG. 10 is a view taken in the direction of arrows along
line X-X in FIGS. 8 and 9, showing a portion where the first and
second exhaust sub-collecting pipes in FIGS. 8 and 9 are
merged;
[0042] FIG. 11 is a perspective view showing another structure of a
joint portion where first and second exhaust pipe collecting pipes
are joined;
[0043] FIG. 12 is a perspective view showing a structure of a
connecting tube to which downstream end portions of the first and
second exhaust sub-collecting pipes in the exhaust pipe collecting
structure in FIG. 11 are connected;
[0044] FIG. 13 is a front view showing another configuration of an
exhaust pipe collecting structure is a view taken in the direction
of arrows along line XIII-XIII in FIG. 14, as seen from the
direction perpendicular to the longitudinal direction of a
crankshaft of the engine;
[0045] FIG. 14 is a plan view showing a configuration of the
exhaust pipe collecting structure in FIG. 13;
[0046] FIG. 15 is a cross-sectional view taken in the direction of
arrows along line XV-XV in FIG. 13, showing a structure of a
cross-section of a joint portion of the exhaust pipe collecting
structure in FIG. 13;
[0047] FIG. 16 is a view taken in the direction of arrows along
line XVI-XVI in FIG. 14, showing a configuration of the exhaust
pipe collecting structure in FIG. 13;
[0048] FIG. 17 is a view taken in the direction of arrows along
line XVII-XVII in FIG. 13, showing a configuration of the exhaust
pipe collecting structure in FIG. 13;
[0049] FIG. 18 is a view taken in the direction of arrows along
line XVIII-XVIII in FIG. 13, showing a configuration of the exhaust
pipe collecting structure in FIG. 13;
[0050] FIG. 19 is a cross-sectional view taken along line IXX-IXX
in FIG. 13, showing a configuration of the exhaust pipe collecting
structure in FIG. 13;
[0051] FIG. 20 is a cross-sectional view taken along line XX-XX in
FIG. 17, showing a configuration of the exhaust pipe collecting
structure in FIG. 17;
[0052] FIG. 21 is a cross-sectional view taken along line XXI-XXI
in FIG. 17, showing a configuration of the exhaust pipe collecting
structure in FIG. 17;
[0053] FIG. 22 is a perspective view showing a structure of a
connecting tube connected to the joint portion of the exhaust pipe
collecting structure in FIG. 18;
[0054] FIG. 23A is a perspective view showing another structure of
the joint portion of the exhaust pipe collecting structure;
[0055] FIG. 23B is a perspective view showing a structure of a
connecting tube connected to the joint portion of the exhaust pipe
collecting structure in FIG. 23A;
[0056] FIG. 24A is a perspective view showing another configuration
of the joint portion of the exhaust pipe collecting structure;
[0057] FIG. 24B is a perspective view showing a structure of a
connecting tube connected to the joint portion of the exhaust pipe
collecting structure in FIG. 24A;
[0058] FIG. 25A is a cross-sectional view taken along line
XXVa-XXVa, showing the structure of the connecting tube in FIG.
22;
[0059] FIG. 25B is a cross-sectional view taken along line
XXVb-XXXb in FIG. 22, showing the structure of the connecting tube
in FIG. 22;
[0060] FIG. 25C is a cross-sectional view taken along line
XXVc-XXVc in FIG. 22, showing the structure of the connecting tube
in FIG. 22;
[0061] FIG. 25D is a cross-sectional view taken along line
XXVd-XXVd in FIG. 22, showing the structure of the joint portion in
FIG. 22;
[0062] FIG. 26 is a side view showing a personal watercraft having
the exhaust pipe collecting structure, according to the present
invention; and
[0063] FIG. 27 is a plan view showing the personal watercraft in
FIG. 26.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0064] Hereinafter, preferred embodiments of an exhaust pipe
collecting structure of the present invention will be described
with reference to the accompanying drawings. Here, a jet-propulsion
personal watercraft will be described.
[0065] In FIGS. 26 and 27, reference numeral A denotes a body of
the personal watercraft. The body A comprises a hull A and a deck D
covering the hull H from above. A line at which the hull H and the
deck D are connected over the entire perimeter thereof is called a
gunnel line G. The gunnel line G is located above the waterline L
of the personal watercraft in a normal condition. As shown in FIG.
27, an opening 16, which has a substantially rectangular shape seen
from above, is formed at a relatively rear section of the deck D
such that it extends in the longitudinal direction of the body A,
and a riding seat S is mounted above the opening 16 such that it
covers the opening 16 from above as shown in FIGS. 26 and 27.
[0066] An engine unit Eu is contained in a chamber (engine room) 20
surrounded by the hull H and the deck D below the seat S and having
a convex-shape in a cross-section of the body A.
[0067] In this embodiment, the engine unit Eu is a multi-cylinder
(four-cylinder) four-cycle engine unit. As shown in FIG. 26, a
crankshaft 26 of the engine E is mounted along the longitudinal
direction of the body A. An output end of the crankshaft 26 is
rotatably coupled integrally with a pump shaft 21S of a water jet
pump P through a propeller shaft 27. An impeller 21 is mounted on
the output shaft 21S of the water jet pump P. The impeller 21 is
covered with a pump casing 21C on the outer periphery thereof. A
water intake 17 is provided on the bottom of the hull H. The water
is sucked from the water intake 17 and fed to the water jet pump P
through a water intake passage 28. The water jet pump P pressurizes
and accelerates the water. The pressurized and accelerated water is
discharged through a pump nozzle 21R having a cross-sectional area
of flow gradually reduced rearward, and from an outlet portion 21K
provided on the downstream end of the pump nozzle 21R, thereby
obtaining the propulsion force.
[0068] In FIG. 26, reference numeral 21V denotes fairing vanes for
fairing water flow inside the water jet pump P. As shown in FIGS.
26 and 27, reference numeral 24 denotes a bar-type steering handle.
By operating the steering handle 24 to the right or to the left,
the steering nozzle 18 provided behind the pump nozzle 21R swings
to the right or to the left through a wire cable 25 as represented
by a dashed line. The watercraft can be turned to any desired
direction while the water jet pump P is generating the propulsion
force. A throttle lever Lt in FIG. 27 serves to adjust an engine
speed of the engine E.
[0069] As shown in FIG. 26, a bowl-shaped reverse deflector 19 is
provided above the rear side of the steering nozzle 18 such that it
can swing downward around a horizontally mounted swinging shaft
19a.
[0070] The deflector 19 is swung downward toward a lower position
behind the steering nozzle 18 to deflect the water ejected from the
steering nozzle 18 forward, and as the resulting reaction, the
personal watercraft moves rearward.
[0071] In FIGS. 26 and 27, reference numeral 22 denotes a rear
deck. The rear deck 22 is provided with an operable hatch cover 29.
A rear compartment (not shown) with a small capacity is provided
under the hatch cover 29. Reference numeral 23 denotes a front
hatch cover. A front compartment (not shown) is provided under the
front hatch cover 23 for storing equipment and the like.
[0072] (Embodiment 1)
[0073] In the four-cylinder engine unit Eu of the personal
watercraft according to this embodiment, ignition takes place in
the order of the first cylinder, the second cylinder, the fourth
cylinder, and the third cylinder. As defined herein, the engine
unit Eu has the engine E, an exhaust pipe collecting structure
(corresponding to the exhaust manifold 1), etc. Since exhaust gases
flow from upstream to downstream, upstream ends 1t of exhaust pipes
1M (1M1 to 1M4) of the exhaust pipe collecting structure 1 are
connected to exhaust ports Ep (see FIG. 2) of cylinders of the
engine E.
[0074] The exhaust pipe collecting structure 1 has a first exhaust
sub-collecting pipe 1A comprised of integral exhaust pipes (see
FIGS. 3 and 5) and a second exhaust sub-collecting pipe 1B
comprised of integral exhaust pipes (see FIGS. 3 and 6). The first
exhaust sub-collecting pipe 1A has two exhaust pipes 1M (1M1, 1M4).
The upstream end 1t of the exhaust pipe 1M1 is attached to the
exhaust port Ep (see FIG. 2) of the first cylinder of the engine E
by means of a bolt (not shown), and the upstream end 1t of the
exhaust pipe 1M4 is attached to the exhaust port Ep (see FIG. 2) of
the fourth cylinder of the engine E by means of a bolt (not
shown).
[0075] The second exhaust sub-collecting pipe 1B has two exhaust
pipes 1M (1M2, 1M3). The upstream end 1t of the exhaust pipe 1M2 is
attached to the exhaust port Ep (see FIG. 2) of the second cylinder
of the engine E by means of a bolt (not shown), and the upstream
end 1t of the exhaust pipe 1M3 is attached to the exhaust port Ep
(see FIG. 2) of the third cylinder of the engine E by means of a
bolt (not shown).
[0076] A first joint portion 1e is provided at a downstream end
portion of the first exhaust sub-collecting pipe 1A. As shown in a
left-side portion in FIG. 4, the first joint portion 1fe has a
semicylindrical peripheral wall opened toward a second joint
portion 1se mentioned later. In other words, the first joint
portion 1fe has a substantially semicircular cross-section with a
circular-arc portion located on the left side in FIG. 4. The second
joint portion 1se is provided at a downstream end portion of the
second exhaust sub-collecting pipe 1B. As shown in a right-side
portion in FIG. 4, the second joint portion 1 se has a
semicylindrical peripheral wall opened toward the first joint
portion 1fe. In other words, the second joint portion 1se has a
substantially semicircular cross-section with a circular-arc
portion located on the right side in FIG. 4.
[0077] As shown in FIG. 4, the first joint portion 1fe and the
second joint portion 1se are combined to each other to allow their
openings to be closed by their opposed joint portions 1e. The
combined joint portions 1e form a wall face of a cylindrical
exhaust pipe having a circular cross-section.
[0078] As shown in FIG. 4, joint faces 1m of the first and second
joint portions 1fe, 1se of the first and second exhaust
sub-collecting pipes 1A and 1B have a plurality of positioning pin
holes through which knock pins Pi are inserted for accurate
relative positioning. An extended face of the joint face 1m has
holes 1k through which joint bolts are inserted. The first and
second joint portions 1fe, 1se are securely fastened to each other
by means of bolts 1r and nuts 1n through the holes 1k. Further, the
joint face 1m has sealing packings 3.
[0079] At the above joint portions 1e, downstream ends of the
exhaust pipes 1M are visible as seen from the downstream ends of
exhaust passages of the joint portions 1e. Specifically, an exhaust
passage 1a connected at its upstream end to the exhaust port Ep
(see FIG. 2) of the fourth cylinder is opened in an upper portion
of the substantially semicircular first exhaust sub-collecting pipe
1A shown on the left side in FIG. 4, and an exhaust passage 1b
connected at its upstream end to the exhaust port Ep (see FIG. 2)
of the first cylinder is opened in a lower portion of the first
exhaust sub-collecting pipe 1A. And, an exhaust passage 1c
connected at its upstream end to the exhaust port Ep (see FIG. 2)
of the third cylinder is opened in an upper portion of the
substantially semicircular second exhaust sub-collecting pipe 1B
shown on the right side in FIG. 4 and an exhaust passage Id
connected at its upstream end to the exhaust port Ep (see FIG. 2)
of the second cylinder in a lower portion of the second exhaust
sub-collecting pipe 1B. In FIG. 4, Is denotes a separating wall
between the exhaust passage 1a and the exhaust passage 1b and a
separating wall between the exhaust passage 1c and the exhaust
passage 1d.
[0080] As described above, the downstream end portion of the first
exhaust sub-collecting pipe 1A and the downstream end portion of
the second exhaust sub-collecting pipe 1B are joined at the joint
face 1m of the joint portions 1e, thereby forming a substantially
cylindrical exhaust passage Q (see. FIG. 3) having a circular
cross-section. The exhaust passage Q has a peripheral wall that
isolates its inside from outside.
[0081] In the exhaust pipe collecting structure 1 configured as
described above, exhaust gases flowing from the four cylinders are
collected into one exhaust passage Q (see FIG. 3) formed by the
joint portions 1e.
[0082] In accordance with the exhaust pipe collecting structure 1
having the above configuration, since the parting plane 1V of the
first exhaust sub-collecting pipe 1A and the parting plane 1V of
the second exhaust sub-collecting pipe 1B are each located on one
continuous plane (see two-dotted lines represented by 1V in FIG.
2), the exhaust pipe collecting structure 1 having a
three-dimensional configuration can be cast using a casting mold.
It will be understood that, as used herein, the term "parting
plane" refers to the surface along which parts of the mold splits
to release a part during the casting process, and is not
necessarily planar. Depending on the type of mold used, the parting
plane may be flat, curved, or a combination thereof. The
double-walled structure of the exhaust pipe collecting structure
shown in FIGS. 3 to 6 is obtained by putting cores in the two-part
casting mold. In this structure, between walls, a water jacket 1J
is formed. The joint portions 1e are not provided with the water
jacket at a downstream end portion 1z. As shown by two-dotted lines
in FIGS. 3 and 4, a rubber tube Gt is provided to cover an outer
periphery of a downstream end portion 1z of the joint portions 1e
and an upstream end portion 55a of an exhaust pipe 55 on a muffler
Mf side to form a cooling water passage (water jacket) 50 between
the outer periphery and the rubber tube Gt, for cooling the tube
Gt, the downstream end portion 1a, and the upstream end portion
55a.
[0083] In the above exhaust pipe collecting structure, the length
of each exhaust passage can be set flexibly as required to improve
exhaust efficiency. Consequently, even in a narrow space, the
exhaust pipe collecting structure with high efficiency is
accommodated.
[0084] When the exhaust pipe collecting structure is cast, the
cooling water jackets 1J are easily formed on the wall portions of
the exhaust passages, i.e., on the outer peripheries of the exhaust
passages. Therefore, even when the exhaust passages are shortened
according to a limited exhaust space within the engine room of the
personal watercraft, the temperature of the exhaust gases is
reduced by the cooling water and the speed of the exhaust gases is
reduced. Thus, the exhaust pipe collecting structure produces the
same effects produced by extending the exhaust passages. In other
words, a power of the engine unit Eu is increased, especially,
torque of the engine is increased.
[0085] As shown in FIG. 1, the exhaust pipe collecting structure 1
is connected to the muffler side (not shown) through the rubber
tube Gt extending to the downstream side. By connecting the exhaust
pipe collecting structure 1 to the exhaust passage located on the
downstream side through the rubber tube Gt, vibration on the engine
E side is inhibited from being transmitted to the muffler or the
like on the downstream side.
[0086] The engine unit Eu comprising the exhaust system having the
above mentioned three-dimensional exhaust pipe collecting structure
has improved exhaust inertia or the like by utilizing the
relationship between the exhaust pipe collecting structure and the
ignition order of the engine unit Eu. The exhaust temperature is
reduced by cooling water flowing around the exhaust passages. As a
result, it is possible to achieve the personal watercraft equipped
with the engine unit having the exhaust pipe collecting structure
with high exhaust efficiency.
[0087] The joint portion 1fe of the first exhaust sub-collecting
pipe 1A and the joint portion 1se of the second exhaust pipe
collecting pipe 1B may be joined by providing a step between the
joint portions 1e, i.e., by deviating the joint face 1m toward the
first exhaust sub-collecting pipe 1A or the second exhaust
sub-collecting pipe 1B (see FIG. 7). Alternatively, as shown in
FIGS. 8 to 10, the joint portions 1e may be combined in a stepless
state.
[0088] (Embodiment 2)
[0089] Referring to FIG. 11, joint portions 101e of first and
second sub-collecting pipes 101A and 101B may be substantially
cylindrical and have joint faces (outer walls) 101m on their side
faces. In this structure, two adjacent exhaust passages Q1 and Q2
are obtained by joining the joint faces 101m. More specifically,
the joint face 101m of the joint portion 101e of the first exhaust
sub-collecting pipe 101A is provided on the right side in FIG. 11
and the joint face 101m of the joint portion 101e of the second
exhaust sub-collecting pipe 101B is provided on the left side in
FIG. 11. These joint faces 101m are in contact with each other and
fastened by means of a bolt and a nut through a bolt inserting hole
101k provided in vertically extending portions of the joint face
101m. In this structure, the sealing packing is unnecessary in the
joint face 101n.
[0090] In FIG. 11, 101a denotes an exhaust passage connected at its
upstream end to the exhaust port of the first cylinder, 101b
denotes an exhaust passage connected at its upstream end to the
exhaust port of the fourth cylinder, 101c denotes an exhaust
passage connected at its upstream end to the exhaust port of the
second cylinder, and 101d denotes an exhaust passage connected at
its upstream end to the exhaust port of the third cylinder. In
addition, 101s denotes a separating wall that defines the exhaust
passage 101a and the exhaust passage 101b and a separating wall
that defines the exhaust passage 101c and the exhaust passage
101d.
[0091] The exhaust passages Q1 and Q2 at the two adjacent joint
portions 101e are connected to a connecting tube 105 to be
collected into an exhaust passage Y. The connecting tube 105 has
branching upstream end portions q1 and q2 connected to the
downstream ends of the exhaust passages Q1 and Q2. As shown in FIG.
12, the connecting tube 105 has a two-part structure with a parting
line 105a extending along the longitudinal direction and is
provided with bolt insertion holes 101h to be securely fastened by
means of bolts and nuts (not shown). Alternatively, although not
shown, an insert-type structure that contains the downstream end
portions of the joint portion 101e may be used.
[0092] In the above structures, as shown in FIG. 12, the rubber
tube Gt covers the outer periphery from the downstream end portion
of the joint portion 101e to the downstream end of the connecting
tube 105 as indicated by two-dotted line. Thereby, a cooling water
passage (water jacket) 50 is formed between the rubber tube Gt and
an outer peripheral face of the joint portion 101e and an outer
peripheral face of the connecting tube 105.
[0093] In this exhaust pipe collecting structure, the effects
provided by the exhaust pipe collecting structure described in the
first embodiment are obtained.
[0094] (Embodiment 3)
[0095] A third embodiment of the present invention will be
described. FIGS. 23A and 23B shows an exhaust pipe collecting
structure 201. The exhaust pipe collecting structure 201 is used in
the four-cylinder engine unit as in the exhaust pipe collecting
structure in FIG. 1. The exhaust pipe collecting structure 201
comprises an exhaust manifold 201Q attached on the engine E and a
connecting tube 201T (tube connecting the exhaust manifold 201Q to
the muffler Mf (see FIG. 27) on the downstream side). The
connecting tube 201T serves to collect a plurality of exhaust
passages into one exhaust passage.
[0096] As shown in FIGS. 13 to 15, the exhaust manifold 201Q of the
exhaust pipe collecting structure 201 is integrally cast.
[0097] The exhaust manifold 201Q comprises exhaust pipes (exhaust
passages) 201M (201M1 to 201M4) that are provided for the
cylinders, respectively, extending from upstream ends 201t
connected to the exhaust ports of the cylinders of the engine E to
downstream end portions of the joint portion 201e which are
connected to the upstream end of the connecting tube 201T.
[0098] As shown in FIGS. 13 and 14, the exhaust pipe 201M1 of the
first cylinder and the exhaust pipe 201M4 of the fourth cylinder
are collected at an intermediate position to be apparently formed
into a first exhaust sub-collecting pipe 201A. The exhaust pipe
201M2 of the second cylinder and the exhaust pipe 201M3 of the
third cylinder are collected at an intermediate position to be
apparently formed into a second exhaust sub-collecting pipe 201B.
As seen from outside, the exhaust manifold 201Q has four branching
upstream end portions and the first exhaust sub-collecting pipe
201A and the second exhaust sub-collecting pipe 201B are collected
in the vicinity of their downstream end portions.
[0099] The joint portion 201e is formed at a position where the
first exhaust sub-collecting pipe 201A and the second exhaust
sub-collecting pipe 201B are collected as seen from outside.
[0100] The exhaust manifold 201Q has an exhaust pipe collecting
structure in which the exhaust pipes 201M1 to 201M4 (on the
upstream side) forming the exhaust manifold 201Q are collected on
the downstream end portion as seen from outside but, in its
internal structure, the exhaust pipes 201M1 to 201M4 are
independent exhaust passages.
[0101] As indicated by an arrow in FIG. 15, a water jacket 20Jq is
formed at the joint portions 201e to have a water flow
cross-section 203 that is elongate in the direction perpendicular
to the parting line of the parting plane in casting (plane
including a boundary 201d between the exhaust sub-collecting pipes
201A and 201B and extending in the depth direction of FIGS. 13 and
14).
[0102] As can be seen from FIG. 15, the water flow cross-section
203 of the water Jacket 201Jq is larger in its longitudinal end
portions than in its intermediate portion. The water flow
cross-section 203 is shaped like a dumbbell. As seen in a
cross-sectional view, the flow cross-section 203 is elongate in the
direction from a portion 201f between the exhaust pipe 201M1 of the
first cylinder and the exhaust pipe 201M4 of the fourth cylinder in
the first exhaust sub-collecting pipe 201A to a portion 201g
between the exhaust pipe 201M2 of the second cylinder and the
exhaust pipe 201M3 of the third cylinder in the second exhaust
sub-collecting pipe 201B.
[0103] Because of the absence of a water jacket between the exhaust
pipe 201M2 of the second cylinder and the exhaust pipe 201M1 of the
first cylinder and between the exhaust pipe 201M3 of the third
cylinder and the exhaust pipe 201M4 of the fourth cylinder, it is
possible to reduce the dimension of the exhaust manifold 201Q in
the direction indicated by an arrow R201 in FIG. 15, in which the
exhaust pipe 201M2 of the second cylinder and the exhaust pipe
201M1 of the first cylinder are arranged and the exhaust pipe 201M3
of the third cylinder and the exhaust pipe 201M4 of the fourth
cylinder are arranged. This leads to reduction in the dimension of
the exhaust manifold 201Q protruding from the side portion of the
engine E.
[0104] The exhaust manifold 201Q according to this embodiment is
provided with a casting parting plane 201V corresponding to a
boundary as indicated by bold two-dotted lines in FIGS. 13, 14, 15,
16, 17, and 18. The casting parting plane 201V is a joint plane of
a mold vertically divided in two in casting.
[0105] The parting plane 201V is located within the same plane at a
position where it is located on a line S1 as seen in a side view
and is located within another planes continuous with the above
plane at a position where it is not located on lines S2 and S3 (see
FIGS. 17 and 18). Specifically, as shown in FIG. 17, the parting
plane 201V is located on different lines S1, S2, and S3, i.e., at
different planes as seen from above in FIGS. 17 and 18, but is
located at different positions in the depth direction in FIG. 17
and is continuous along an inclined (or curved) plane in the depth
direction in FIG. 17. Also, when the lines S2 and S3 are located at
different positions in the depth direction, the parting plane 201V
including the lines S2 and S3 is continuous along the inclined (or
curved) plane in the depth direction in FIGS. 17 and 18. In this
structure, the whole parting plane is continuous in three
dimensions.
[0106] For the above reasons, the entire exhaust manifold 201Q can
be integrally cast.
[0107] In accordance with the exhaust manifold (exhaust pipe
collecting structure) shown in this embodiment, the parting plane
201V is located on substantially the straight line within a small
dimension in the lateral direction (thickness direction of the
exhaust manifold 201Q (see the direction indicated by an arrow D2)
as shown in FIGS. 17 and 18. This makes the exhaust manifold 201M
compact. The exhaust manifold 201Q is thin in the thickness
direction thereof (see D2 in FIGS. 17 and 18). In spite of the
compact structure, each of the exhaust pipes 201M has a
double-walled structure, and around each of the exhaust pipe 201M,
the water jacket 201Jq is formed.
[0108] FIG. 19 shows the cross-section of the exhaust manifold 201Q
taken along line IXX-IXX in FIG. 13 and FIG. 20 shows the
cross-section of the exhaust manifold 201Q taken along line XX-XX
in FIG. 17. Likewise, FIG. 21 shows the cross-section of the
exhaust manifold 201Q taken along line XXI-XXI in FIG. 17. In FIGS.
19, 20, and 21, 201M1 denotes the exhaust pipe of the first
cylinder, 201M2 denotes the exhaust pipe of the second cylinder,
201M3 denotes the exhaust pipe of the third cylinder, and 201M4
denotes the exhaust pipe of the fourth cylinder. In these Figures,
201Jq denotes water jackets.
[0109] As shown in FIGS. 14 and 16, a flange 201R is provided at
the upstream ends 201t of the exhaust manifold 201Q to be attached
to the engine. As shown in FIG. 16, the flange 201R is provided
with mounting holes 201h through which the flange 201R is fastened
to the engine by means of bolts, and cooling ports 201w through
which water from the water jacket 201Jq flows toward the water
jacket on the engine side, or the water flows in the opposite
direction.
[0110] As shown in FIG. 16, a flange 201F is provided at a
downstream end of the joint portion 201e of the exhaust manifold
201Q to be connected to the connecting tube T (see FIG. 22). The
flange 201R is also provided with mounting holes 201h through which
the flange 201R is fastened to the engine by means of bolts and
cooling ports 201w through which water from the water jacket 201Jq
flows toward the water jacket 201Jt of the connecting tube 201T
(see FIG. 22) located on the downstream side, or the water flows in
the opposite direction (see FIG. 22). The cooling ports 201w
correspond to an end face of the water jacket 201Jq.
[0111] In FIG. 18, 209 denotes a cooling water supply port through
which cooling water is supplied to cooling ports 201wg and the
water jacket 201Jq of the exhaust manifold 201Q.
[0112] In the exhaust pipe collecting structure 201, the flange
(joint portion) 201F of the exhaust manifold 201Q is connected to a
connecting tube 201T in FIG. 22.
[0113] A connecting end face 240 of the connecting tube 201T, which
is connected to the flange 201F (see FIG. 16) is structured as
follows. At the connecting end face 240 of the connecting tube
201T, the water jacket 201Jt is located at a center thereof to
extend obliquely rightwardly in FIG. 22 and serves to cool an
inside of the connecting tube 201T. The water jacket 201Jt of the
connecting tube 201T is connected to the water jacket 201Jq of the
exhaust manifold 201Q shown in FIG. 15 or 18 such that the
longitudinal axes of water flow cross-sections 203 and 243 of the
water jackets 201Jq and 201Jt cross each other. Typically, the
longitudinal axes of water flow cross-sections 203 and 243 make an
angle of 90 degrees.
[0114] Furthermore, as shown in FIG. 22, in the connecting end face
240, an end face of a first connecting exhaust passage 241M1
connected to the exhaust pipe 201M1, an end face of a fourth
connecting exhaust passage 241M4 connected to the exhaust pipe
201M4, an end face of a second connecting exhaust passage 241M2
connected to the exhaust pipe 201M2, and an end face of the third
connecting exhaust passage 241M3 connected to the exhaust pipe
201M3 are opened.
[0115] At the connecting end face 240 in FIG. 22, the water flow
cross-section 243 of the water jacket 201Jt is elongate in the
direction from a portion 241f between the first connecting exhaust
passage 241M1 and the second connecting exhaust passage 241M2 to a
portion 241g between the fourth connecting exhaust passage 241M4
and the third connecting exhaust passage 241M3. The water flow
cross-section 243 is like a dumbbell.
[0116] As indicated by a broken line in FIG. 22, the first
connecting exhaust passage 241M1 and the fourth connecting exhaust
passage 241M4 are collected at a merging point 251 located upstream
of a downstream end portion (right upper end in FIG. 22) of the
connecting tube 201T into a first collecting exhaust passage
(exhaust sub-collecting pipe) 241A, and the second connecting
exhaust passage 241M2 and the third connecting exhaust passage
241M3 are collected at a merging point 252 located upstream of the
end portion into a second collecting exhaust passage (exhaust
sub-collecting pipe) 241B.
[0117] Finally, the first collecting exhaust passage 241A and the
second collecting exhaust passage 241B are collected at a merging
point 253 in the vicinity of the end portions into a single exhaust
passage 241C. The merging point 253 is positioned downstream of the
merging points 251 and 252.
[0118] Another water jackets 201Wt provided at eight positions in a
peripheral portion of the connecting tube 201T are connected to the
cooling ports wg provided in a peripheral portion on the exhaust
manifold 201Q in FIG. 15 to allow cooling water to flow
therethrough.
[0119] The variation in the cross-sectional shape of the exhaust
passages and water jacket 201Jq of the connecting tube 201T which
are sectioned in the direction perpendicular to a flow of the
exhaust gases is as follows. The cross-section taken along line
XXVa-XXVa in FIG. 22 is shown in FIG. 25A, the cross-section taken
along line XXVb-XXVb in FIG. 22 is shown in FIG. 25B, the
cross-section taken along line XXVc-XXVc in FIG. 22 is shown in
FIG. 25C, and the cross-section taken along line XXVd-XXVd in FIG.
22 is shown in FIG. 25D.
[0120] In the connecting tube 201T having the above structure,
because of the absence of the water jackets 201Jt between the first
connecting exhaust passage 241M1 and the fourth connecting exhaust
passage 241M4 and between the second connecting exhaust passage
241M2 and the third connecting exhaust passage 241M3, the water
jacket 201Jt having the water flow cross-section 243 is extended to
the downstream portion of the connecting tube 201T. More
specifically, the water jacket 201Jt extends to pass through the
merging point 251 where the first connecting exhaust passage 241M1
and the fourth connecting exhaust passage 241M4 are merged and the
merging point 252 where the second connecting exhaust passage 241M2
and the third connecting exhaust passage 241M3 are merged, and to
its downstream region located upstream of the merging point 253
where the first collecting exhaust passage 241A and the second
collecting exhaust passage 241B are merged. As a result, cooling
capability of the connecting tube 201T is improved.
[0121] As shown in FIG. 22, it is also possible to reduce the
dimension of the connecting tube 201T in the direction indicated by
an arrow D3 in FIG. 22 in which the first connecting exhaust
passage 241M1 and the fourth connecting exhaust passage 241M4 (the
second connecting exhaust passage 241M2 and the third connecting
exhaust passage 241M3) are arranged. This reduces the dimension of
the connecting tube 201T protruded from the side portion of the
engine E is reduced with the exhaust manifold 201Q and the
connecting tube 201T mounted on the engine.
[0122] In the structure in which the longitudinal axis of the water
jacket jq of the exhaust manifold 201Q (see FIG. 18) crosses the
longitudinal axis of the water jacket jt of the connecting tube
201T, as shown in FIGS. 23A and 23B, a water flow cross-sectional
portion 248 that is enlarged in substantially circular shape is
located at center positions of the water flow cross-sections to
increase a water flow cross-sectional area. So, at the connecting
portion between the water jackets jq and jt with their longitudinal
axes crossing each other, a sufficient water flow-cross sectional
area is obtained. In this structure, at the connecting portion, the
cooling water smoothly flows.
[0123] Instead of the substantially circular shape, other shapes
including an oval shape, a rectangular shape, etc may be used as
the shape to increase the water flow cross-sectional area.
Alternatively, as shown in FIG. 24B, a circular water flow portion
248 may be exposed in the connecting end face 240 of the connecting
tube 201T, and inside the connecting tube 201T, the downstream
portion of the circular water flow portion 248 may be connected to
the dumbbell-shaped water flow portion 248 of the water jacket
201Jq of the exhaust manifold 201Q. In this structure, an end face
portion of the water jacket 201Jq of the exhaust manifold 201Q is
closed by the connecting end face 240 of the connecting tube 201T
except the circular water flow portion. Alternatively, at the
position where the water jacket 201Jq of the exhaust manifold 201Q
is connected to the water jacket 201Jt of the connecting tube 201T,
the water flow portion 248 of the water jacket 201Jq may be
circular to conform in shape to that of the connecting tube 201T.
Further, alternatively, in the configuration shown in FIGS. 23A and
23B, a packing member (seal member) is provided in the connecting
face to have the circular hole to allow the cooling water to flow
from the exhaust manifold 201Q to the connecting tube 201T
therethrough.
[0124] While the exhaust manifold and the connecting tube are
independent of each other, they may be integral with each other. In
this structure, the water jacket having the above structure is
formed inside the exhaust pipe collecting structure in which the
exhaust manifold and the connecting tube are integral with each
other.
[0125] The above-described embodiments may be applied to an exhaust
pipe collecting structure of a two-cycle engine, in addition to the
four-cycle engine, in which case the same function and effects are
provided. Further, the embodiments may be applied to four cylinders
of six cylinders, four cylinders of eight cylinders, four cylinders
of ten cylinders, four cylinders of twelve cylinders, etc, and the
same function and effects are provided.
[0126] The exhaust pipe collecting structure of the present
invention may be used in exhaust pipe collecting structures of
engine units of vehicles other than the personal watercraft; for
example, a small all-terrain vehicle.
[0127] Numerous modifications and alternative embodiments of the
invention will be apparent to those skilled in the art in view of
the foregoing description. Accordingly, the description is to be
construed as illustrative only, and is provided for the purpose of
teaching those skilled in the art the best mode of carrying out the
invention. The details of the structure and/or function may be
varied substantially without departing from the spirit of the
invention and all modifications which come within the scope of the
appended claims are reserved.
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